CN104651833A - Repairing method and device for concave-convex defect of inside-laser powder feeding cladding - Google Patents

Abstract

The invention discloses a repairing method and device for a concave-convex defect of inside-laser powder feeding cladding. The repairing method comprises the following steps of S1, controlling a concave point in a concave-convex defect surface of a base material to be located on an initial negative defocusing position of an annularly-tapered focused laser beam; S2, controlling the annularly-tapered focused laser beam, a powder beam located inside the laser beam and a protective gas located at the periphery of the powder beam to coaxially emit; S3, controlling the laser beam, the powder beam located inside the laser beam and the protective gas located at the periphery of the powder beam to move along the concave-convex defect surface; and S4, melting the powder beam on the surface of the material by using the laser beam, solidifying to form a cladding runner, and repeatedly moving to repair the concave-convex defect step by step in a layer-by-layer cladding way. The repairing method disclosed by the invention is used for repairing the concave-convex defect surface of the base material based on hollow laser and inside-laser powder feeding; and meanwhile, an even cladding layer is formed on the concave-convex defect surface through reasonably controlling the defocusing amount of laser, so that the unevenness caused by accumulation on a forming surface in a cladding accumulation forming process is repaired.

Description

Repair method and repair device for concave and convex defects in laser light internal powder feeding cladding

technical field

The invention relates to the technical field of laser cladding three-dimensional forming, in particular to a method and a corresponding device for repairing concave-convex defects in the laser cladding process.

Background technique

Laser cladding three-dimensional forming technology is to irradiate the laser beam on the processing surface to form a molten pool on the surface of the metal material, and simultaneously send the powder beam into the molten pool. The laser melts the powder and moves on the processed surface, and the molten pool is continuously solidified to form a molten channel. This technology can realize moldless, fast, full-dense near-net shape of high-performance metal parts, and has developed rapidly in aerospace, metallurgy, mining, machinery manufacturing and other industries.

In the process of cladding accumulation forming, process control is a very important aspect. Often during the first few layers of material build-up, the forming surface may experience undulations. At this time, if it cannot be controlled, unevenness will appear on the surface after several layers are piled up, which will seriously affect the forming quality, and even make the accumulation and forming process unable to continue.

Therefore, in view of the above problems, it is necessary to propose a further solution.

Contents of the invention

In view of this, the present invention provides a method and a corresponding device for repairing concave-convex defects in the laser cladding process, so as to overcome the deficiencies in the prior art.

In order to achieve the above object, the technical solutions provided by the embodiments of the present invention are as follows:

A method for repairing concave-convex defects in laser light internal powder feeding cladding, which comprises the following steps:

S1. Controlling the concavo-convex defect surface of the base material to locate the concave point at the initial negative defocus position of the annular conical focused laser beam, and the initial negative defocus is 2-4mm;

S2. Control the conical focused laser beam, the powder beam located inside the conical focused laser beam, and the shielding gas located on the periphery of the powder beam to exit coaxially, and shoot to the concave-convex defect surface of the base material;

S3. Control the ring-shaped focused laser beam, together with the powder beam inside it, and the shielding gas around the powder beam to move along the surface of the concave-convex defect. The negative defocus amount of the shaped focused laser beam changes from small to large;

S4. The ring-shaped conical focused laser beam melts the powder beam on the surface of the material and solidifies into a layer of melting channel, which moves repeatedly, and gradually repairs the concave-convex defects by layer-by-layer cladding.

As an improvement of the method for repairing concave-convex defects in laser light internal powder feeding cladding of the present invention, the powder beam is located at the axis of the conical focused laser beam, and the diameter of the powder beam is 2mm;

As an improvement of the method for repairing concave-convex defects in laser light internal powder feeding cladding of the present invention, in the step S3, the scanning speed of the annular conical focused laser beam is 4-6mm/s, and the powder supply rate of the powder beam is 7- 9g/min, the carrier gas flow rate of shielding gas is 2.5-3.5L/min.

In order to achieve the above object, the present invention also provides a repairing device for concave-convex defects in the laser cladding process, which includes: a high-power fiber laser system, a robot system, a powder feeder, an internal powder feeding nozzle, and a protective gas delivery system;

The optical internal powder feeding nozzle is used to emit ring-shaped focused laser beams, and the optical internal powder feeding nozzle is connected to the high-power fiber laser system; the powder feeder and shielding gas delivery system are connected to the cladding The optical head is connected, the powder feeder includes a powder injection tube, and the powder injection tube is arranged at the center of the annular conical focused laser beam and coaxially arranged with the annular conical focused laser beam, and the protective gas delivery system The conveyed shielding gas is formed at the periphery of the powder beam.

Compared with the prior art, the beneficial effects of the present invention are: the method for repairing concave-convex defects in the laser cladding process of the present invention is based on hollow laser and optical internal powder feeding to repair the concave-convex defect surface of the base material, and at the same time, through reasonable control The amount of laser defocus can form a smooth cladding layer on the surface of concave-convex defects, and repair the unevenness of the forming surface due to accumulation during the process of cladding accumulation forming. The width of the repaired cladding layer changes little; the structure is relatively uniform and dense, and the hardness shows a steady downward trend from top to bottom.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments described in the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is the graph of the relationship between the negative defocus amount of the laser and the thickness of the corresponding cladding layer;

Fig. 2 is the photo after adopting the repairing method of concave-convex defect in the laser cladding process of the present invention to pile up multi-layer cladding layer;

Fig. 3 is the photo after adopting the method in the comparative example to pile up multi-layer cladding layer;

Fig. 4 is the cross-sectional view of the sample obtained by cutting the sample from the multi-layer cladding layer in Fig. 2;

Fig. 5 is the scanning electron micrograph of place a in the internal organization of sample among Fig. 4;

Fig. 6 is the scanning electron micrograph of b place in the inner structure of sample among Fig. 4;

Fig. 7 is the scanning electron micrograph of c place in the inner structure of sample among Fig. 4;

Fig. 8 is the microhardness curve to the direction close to the matrix material from the surface of the multi-layer cladding layer deposited by the method of the present invention;

Fig. 9 is the change curve of the width of any thin-walled wall after the thin-walled wall is repaired by the method of the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described The embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

The method for repairing the concave-convex defect in the laser cladding process of the present invention comprises the following steps:

S1. Controlling the concavo-convex defect surface of the base material to locate the concave point at the initial negative defocus position of the annular conical focused laser beam, and the initial negative defocus is 2-4mm;

S2. Control the conical focused laser beam, the powder beam located inside the conical focused laser beam, and the shielding gas located on the periphery of the powder beam to exit coaxially, and shoot to the concave-convex defect surface of the base material;

S3. Control the ring-shaped focused laser beam, together with the powder beam inside it, and the shielding gas around the powder beam to move along the surface of the concave-convex defect. The negative defocus amount of the shaped focused laser beam changes from small to large;

S4. The ring-shaped conical focused laser beam melts the powder beam on the surface of the material and solidifies into a layer of melting channel, which moves repeatedly, and gradually repairs the concave-convex defects by layer-by-layer cladding.

Specifically, before the step S1, it also includes: before repairing the concave-convex defect surface of the base material, it needs to be pre-treated. The pre-treatment specifically includes: using sandpaper to polish the concave-convex defect surface, removing oil stains with alcohol, and then cleaning with acetone, and then placing in an oven at 200° C. for 2 hours to remove water.

In the step S2, the annular conical focused laser beam, the shielding gas and the powder beam are emitted coaxially, and irradiated on the surface of the concave-convex defect, so that the powder beam is melted and deposited on the corresponding surface under the action of the laser, forming a molten cladding.

Specifically, the ring-cone focused laser beam is a hollow laser. Here, the hollow laser means that the emitted laser is ring-shaped. Therefore, the optical powder feeding refers to feeding the powder to be sprayed inside the ring laser. Further, the laser is an annular beam, the sprayed powder beam is located at the axis of the annular beam, and the protective gas is located at the periphery of the powder beam, forming a protective air curtain. Preferably, the powder, the ring laser, and the protective gas curtain are arranged coaxially. Wherein, the sprayed powder forms a powder beam, which is straight and less divergent, and its diameter is preferably 2mm.

The powder to be sprayed can be Fe313 alloy powder with a particle size of 75-106 μm, and the alloy powder includes 0.1% carbon, 2.5-3.5% silicon, 13.0-17.0% chromium, and 0.5-1.5 boron by weight percentage. %, the rest is iron.

In addition, in step S2, the scanning speed of the laser is 5 mm/s, the power supply rate is 8 g/min, and the flow rate of the carrier gas is 3 L/min.

In the step S3, the negative defocus amount refers to the absolute value of the negative defocus.

As shown in Figure 1, it is a curve diagram of the relationship between the negative defocus amount of the ring conical focused laser beam and the thickness of the corresponding cladding layer. It can be seen from the figure that with the negative defocus of the ring conical focused laser beam As the amount decreases, the diameter of the ring-shaped spot increases gradually. Correspondingly, the molten pool becomes larger, and the powder entering the molten pool increases. Therefore, the thickness of the single-layer cladding layer increases accordingly. When the defocus amount reaches about -3mm, the power density of the annular conical focused laser beam, the duty ratio of the annular spot and the size of the powder spot achieve the best coupling, and the thickness of the single-layer cladding layer is the highest at this time. As the negative defocus of the conical focused laser beam further decreases, the diameter of the spot is gradually larger than the diameter of the powder spot of 2mm. At this time, the area of the molten pool gradually expands, but the amount of powder entering the molten pool cannot increase accordingly, so The thickness of the single-layer cladding layer will gradually decrease.

Therefore, based on the above analysis, in the repair method of the present invention, during the process of irradiating the concave-convex defect surface of the base material with the laser emitted by the cladding bald head, the defocus amount of the annular conical focused laser beam is in the interval of [-3mm,-5mm] range gradually decreases. In this way, when the laser is irradiated on the concave part of the surface of the concave-convex defect, the cladding layer formed will fill it. The thickness is correspondingly reduced, and correspondingly, the thickness of the cladding layer at the protrusion is correspondingly reduced. Therefore, after accumulating multiple cladding layers, the height difference between the depression and the protrusion can be gradually eliminated, so that the surface of the concave-convex defect tends to be flat.

The method for repairing concave-convex defects in the laser cladding process of the present invention is tested below in combination with test experiments.

In this test experiment, three raised fence-shaped thin-walled walls were set on the surface of the base material. The height of the three raised fence-shaped thin-walled walls was 2mm and the distance between them was 10mm, which was used as the concave-convex defect surface.

According to the repairing method of the present invention, the defocusing amount of the laser is gradually reduced within the range of [-3mm, -5mm] during the process of irradiating the three raised fence-like thin walls.

As shown in Fig. 2, it is a photo of a multi-layer cladding layer deposited by the method of the present invention. It can be seen from Fig. 2 that as the cladding layer continues to increase, the morphology tends to gradually stabilize.

Similarly, three raised fence-shaped thin-walled walls are additionally set on the surface of the base material. The height of the three raised fence-shaped thin-walled walls is 2mm, and the distance between them is 10mm, so as to serve as the concave-convex defect surface.

In the process of irradiating the three raised fence-like thin walls, the defocusing amount of the laser gradually decreases within the range of [-0mm,-3mm].

As shown in Figure 3, it is a photo of the multi-layer cladding layer deposited by the method in the comparative example. It can be seen from Figure 3 that as the number of accumulated layers increases, the unevenness of the appearance becomes more and more obvious, and there is no repair effect. Effect.

For the multi-layer cladding layer deposited by the method of the present invention, samples were cut along the cross section perpendicular to the laser scanning direction, mounted and polished, and the overall outline and internal structure were observed with a scanning electron microscope (SEM).

As shown in Figure 4, it is a cross-sectional view of the cut sample. It can be seen that the overall outline is relatively regular and the edges tend to be flat.

As shown in Figures 5 to 7, they are the scanning electron micrographs of the internal structures a, b, and c of the sample cut in Figure 4, respectively. It can be seen from Figure 5 that the fusion boundary bends toward the inside of the base material, and a good metallurgical bond is formed between the cladding layer and the base material; as shown in Figures 6 and 7, the internal structure of the cladding layer is dense and uniform, with obvious vertical to the interface Dendrite growth characteristics.

As shown in Figure 8, it is the microhardness curve for the surface of the multi-layer cladding layer deposited by the method of the present invention to the direction close to the base material. It can be seen from the figure that the hardness shows a downward trend, and the hardness distribution is uniform and the change is relatively large. smooth.

As shown in Figure 9, it is the width change curve of any thin-walled wall after the thin-walled wall is repaired by the method of the present invention. It can be seen from the figure that with the increase of cladding layers, the width of the thin-walled wall has a slight decrease. This is due to the slight error in the single-layer thickness and lifting amount when each layer is stacked, but the overall width of the thin-walled wall does not change much.

The present invention also provides a repairing device for concave-convex defects in the laser cladding process, which is used to realize the above-mentioned repairing method. Specifically, the repair device includes: a high-power fiber laser system, a robot system, a powder feeder, an internal optical powder feeding nozzle, and a protective gas delivery system;

Wherein, the optical internal powder feeding nozzle is used to emit a conically focused laser beam, and the optical internal powder feeding nozzle is connected to the high-power fiber laser system; the powder feeder and the shielding gas delivery system are connected to the The cladding optical head is connected, the powder feeder includes a powder injection tube, and the powder injection tube is arranged at the center of the annular conical focused laser beam and coaxially arranged with the annular conical focused laser beam, and the shielding gas The shielding gas conveyed by the conveying system is formed on the periphery of the powder beam. In this way, the coaxial injection of powder, laser and shielding gas can be realized.

In summary, the method for repairing concave-convex defects in the laser cladding process of the present invention is based on hollow laser and optical powder feeding to repair the concave-convex defect surface of the base material. A flat cladding layer is formed, which repairs the unevenness of the forming surface due to accumulation during the process of cladding accumulation forming. The width of the repaired cladding layer changes little; the structure is relatively uniform and dense, and the hardness shows a steady downward trend from top to bottom.

It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the present invention. Any reference sign in a claim should not be construed as limiting the claim concerned.

In addition, it should be understood that although this specification is described according to implementation modes, not each implementation mode only contains an independent technical solution, and this description in the specification is only for clarity, and those skilled in the art should take the specification as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

Claims (4)

1. a method for repairing powder-feeding cladding concave-convex defect in laser light, it is characterized in that, described method for repairing comprises the following steps: S1. Controlling the concavo-convex defect surface of the base material to locate the concave point at the initial negative defocus position of the annular conical focused laser beam, and the initial negative defocus is 2-4mm; S2. Control the conical focused laser beam, the powder beam located inside the conical focused laser beam, and the shielding gas located on the periphery of the powder beam to exit coaxially, and shoot to the concave-convex defect surface of the base material; S3. Control the ring-shaped focused laser beam, together with the powder beam inside it, and the shielding gas around the powder beam to move along the surface of the concave-convex defect. The negative defocus amount of the shaped focused laser beam changes from small to large; S4. The ring-shaped conical focused laser beam melts the powder beam on the surface of the material and solidifies into a layer of melting channel, which moves repeatedly, and gradually repairs the concave-convex defects by layer-by-layer cladding. 2. The method for repairing concave-convex defects in laser light internal powder feeding cladding according to claim 1, wherein the powder beam is located at the axial center of the conical focused laser beam, and the diameter of the powder beam is 2mm. 3. The method for repairing concave-convex defects in laser light internal powder feeding cladding according to claim 1, characterized in that, in the step S3, the scanning speed of the annular conical focused laser beam is 4-6mm/s, and the powder beam The powder supply rate is 7-9g/min, and the carrier gas flow rate of the protective gas is 2.5-3.5L/min. 4. A repairing device for realizing the repairing method for concave-convex defects in laser light internal powder feeding cladding according to any one of claims 1-3, characterized in that, the repairing device comprises: a high-power fiber laser system, a robot system, Powder feeder, light internal powder feeding nozzle, protective gas delivery system; The optical internal powder feeding nozzle is used to emit ring-shaped focused laser beams, and the optical internal powder feeding nozzle is connected to the high-power fiber laser system; the powder feeder and shielding gas delivery system are connected to the cladding The optical head is connected, the powder feeder includes a powder injection tube, and the powder injection tube is arranged at the center of the annular conical focused laser beam and coaxially arranged with the annular conical focused laser beam, and the protective gas delivery system The conveyed shielding gas is formed at the periphery of the powder beam.